Ankle injuries typically involve fractures of the tibia and fibula, malleolar fractures, and strain, tearing or rupture of one or more connective ligaments. After reduction of the fracture and repair of ligaments, the injury is treated by holding the foot in a neutral position and immobilizing the ankle in a rigid cast from below the knee to the toes. The rigid cast, which is typically molded plaster or resin, is replaced from time to time over a period of several weeks as swelling is reduced. Such rigid casts are heavy, limit the mobility of the patient, and may cause joint stiffening and muscle atrophy.
After the injured joint has stabilized, it has been found that recovery and rehabilitation can be improved by gradually permitting the injured joint to bear progressively more weight during walking movement. Traditionally, this has been carried out by replacing the bent knee long-leg cast with a tibial walking cast. Typically, two or more walking casts may be required over the course of full recovery to accommodate shrinking of the limb caused by muscle atrophy. That is, due to the rigid nature of the molded plaster or resin casts, any loosening which may result from reduction of swelling or muscle atrophy will require cast replacement to maintain the snug fit required to insure that the fracture heals in the neutral position.
Moreover, it will be appreciated that because of the rigid nature of the molded cast, wound treatment procedures, bathing and skin treatment must be postponed until the cast is removed.